Classes and Objects

We have previously looked at two paradigms of programming - imperative (using statements, loops, and functions as subroutines), and functional (using pure functions, higher-order functions, and recursion).

Another very popular paradigm is object-oriented programming (OOP).

Objects are created using classes, which are actually the focal point of OOP.

The class describes what the object will be, but is separate from the object itself. In other words, a class can be described as an object’s blueprint, description, or definition.

You can use the same class as a blueprint for creating multiple different objects.

Classes are created using the keyword class and an indented block, which contains class methods (which are functions).

class Cat:
  def __init__(self, color, legs):
    self.color = color
    self.legs = legs

felix = Cat("ginger", 4)
rover = Cat("dog-colored", 4)
stumpy = Cat("brown", 3)

Accessing Object Variables:

To access the variable inside of the newly created object “myobjectx” you would do the following:

class MyClass:
    variable = "blah"

    def function(self):
        print("This is a message inside the class.")

myobjectx = MyClass()

myobjectx.variable

You can create multiple different objects that are of the same class(have the same variables and functions defined). However, each object contains independent copies of the variables defined in the class.

Accessing Object Functions

To access a function inside of an object you use notation similar to accessing a variable:

class MyClass:
    variable = "blah"

    def function(self):
        print("This is a message inside the class.")

myobjectx = MyClass()

myobjectx.function()